Portable tools of the type forming the subject matter of this application are usually percussion tools; that is, pneumatically powered and comprise such mechanisms as hammers, chippers, drills, grinders and the like; although, there are a rather large variety of tools powered by small internal-combustion engines; e.g., grass and weed trimmers of the string type. Of all tools of this general class, the pneumatic hammers and chisels or chippers are the worst offenders in the area of creating vibrations of such magnitude as to cause relatively serious traumatic conditions in the users, the most common of which is the occupationally-disabling vibration syndrome. Numerous studies of and attempted solutions to the vibration problem have been essayed, directed mainly to the provision of various forms of shock-absorbing materials interposed between the tool handle and the moving part of the tool. Typical of such part-solutions is the disclosure in the Shotwell U.S. Pat. No. 3,968,843, wherein a block of rubber is disposed between the handle and barrel of a pneumatic percussion tool.